Mono-, di-, and trimetallic complexes of the nonalternating polycondensed pi-perimeter decacyclene, C36H18: synthesis, structure, and spectroelectrochemistry of

Reaction of the half-sandwich complexes [(eta5-Me4RC5)M(eta2:O-acac)] (M = Co, Ni; R = Me or Et) with di- and trianions of the polycondensed pi-hydrocarbon decacyclene results in formation of the first Co and Ni triple-decker complexes of this hydrocarbon. For the title compound NMR spectra as well as a crystal structure analysis reveal an antarafacial coordination of two (eta5-Me4EtC5)Co fragments at the central six-membered ring and one of the neighboring five-membered rings of decacyclene. The bridging pi-perimeter decacyclene displays a bowl-shaped topology. In the case of Ni, coordination of two (eta5-Me5C5)Ni fragments at the central six-membered ring of decacyclene is observed, based on the results of 1H and 13C NMR studies. This coordination mode is without precedent for nickel organometallic compounds reported so far. The cobalt complex shows a rich spectroelectrochemistry. Results of cyclic voltammetry and coupled ESR experiments reveal a strong interaction of both metal centers in the mixed-valent monocation of [(eta5-Me4EtC5)Co2(mu-eta5:eta4-C36H18)]. This categorizes the title compound into Robin Day class III.

Synthesis, structure, and spectroelectrochemical investigation of novel ternary Co/S(Se)/Sn clusters derived from binary cobalt stannanediyl complexes.

The synthesis and structure of heterobimetallic Co/Sn complexes [(eta5-CpR)Co-Sn[CH(SiMe3)2]2] (CpR = C5Me5 2; C5EtMe4 3) are described. Insertion reactions of sulfur and selenium into the unbridged heteronuclear Co-Sn bonds of 1, 2, and 3 (R= H5 1, Me5 2, EtMe4 3) have been studied. Depending on the stoichiometry of the chalcogen element used, novel ternary Sn-chalcogen-Co clusters (8, 9, 15, and 16) can be synthesized, and their molecular structures, which represent rare examples of crystallographically characterized cases of ternary transition metal/chalcogen/tin complexes, have been determined. Electrochemistry shows that complexes 8 and 9 are able to support reversibly either the removal or addition of one electron. Insertion of a further (Cp)Co-E (E = chalcogen) fragment significantly affects the electron distribution and causes complexes 9 and 16 to undergo two consecutive one-electron oxidations. The EPR spectra of the respective monocations have been recorded. In all cases, the unpaired electron strongly interacts with the cobalt nucleus(i), thus testifying that the main contribution to the relevant HOMO orbitals comes from the cobalt atom(s).

Impaired antibody levels to tetanus toxoid and pneumococcal polysaccharides in acute leukemias.

Antibody levels to the protein antigen tetanus toxoid (TTx) and the carbohydrate antigens pneumococcal capsular polysaccharides (PCP) were studied by enzyme immunoassay in 14 patients with acute lymphocytic leukemia (ALL) and 32 patients with acute non lymphocytic leukemia (ANLL) before and three weeks after initiation of chemotherapy. The antibody levels to TTx were significantly lower in ALL patients than in controls. This was associated with elevated levels of sCD8 (soluble CD8) in the serum of 12 out of the 14 ALL patients. Patients with ANLL had normal antibody levels before chemotherapy. After chemotherapy ANLL patients with septic complications had a reduced increase of antibody titers to TTx than patients without sepsis. The average antibody titers to PCP decreased in patients with sepsis, while they increased slightly in patients without sepsis. We conclude that in contrast to ANLL patients ALL patients have preexisting decreased antibody levels to thymus dependent protein antigens, while antibody levels to thymus independent carbohydrate antigens are normal in both types of leukemias.